C# Exception handling. Handling Errors during the Program Execution

Agenda

What are Exceptions?
Handling Exceptions
The System.Exception Class
Types of Exceptions and their Hierarchy
Raising

What are Exceptions?

The exceptions in .NET Framework are classic implementation of

Handling Exceptions

In C# the exceptions can be handled by the try-catch-finally

Handling Exceptions – Example

static void Main()
{
string s = Console.ReadLine();
try

The System.Exception Class

Exception is a base class for all exceptions
Important properties:
Message

Exception Properties – Example

class ExceptionsExample
{
public static void CauseFormatException()
{
string

Exception Properties

The Message property gives brief description of the problem
The StackTrace

Exception Properties (2)

File names and line numbers are accessible only if

Exception Hierarchy

Exceptions in .NET Framework are organized in a hierarchy

Types of Exceptions

.NET exceptions inherit from System.Exception
The system exceptions inherit from

Handling Exceptions

When catching an exception of a particular class, all its

Find the Mistake!

static void Main()
{
string s = Console.ReadLine();
try
{

Handling All Exceptions

All exceptions thrown by .NET managed code inherit the

Throwing Exceptions

Exceptions are thrown (raised) by throw keyword in C#
Used to

How Exceptions Work?

Main()

Method 1

Method 2

Method N

2. Method call

3. Method call

4. Method

Using throw Keyword

Throwing an exception with an error message:
Exceptions can accept

Re-Throwing Exceptions

Caught exceptions can be re-thrown again:

try
{
Int32.Parse(str);
}
catch (FormatException fe)
{
Console.WriteLine("Parse

Throwing Exceptions – Example

public static double Sqrt(double value)
{
if (value <

Choosing the Exception Type

When an invalid parameter is passed to a

The try-finally Statement

The statement:
Ensures execution of given block in all cases
When

try-finally – Example

static void TestTryFinally()
{
Console.WriteLine("Code executed before try-finally.");
try
{

Exceptions – Best Practices

catch blocks should begin with the exceptions

Exceptions – Best Practices (2)

When raising an exception always pass to

Exceptions – Best Practices (3)

Exceptions can decrease the application performance
Throw exceptions

Summary

Exceptions provide flexible error handling mechanism in .NET Framework
Allow errors to